A valve timing controller controls opening-and-closing timing of an intake valve or an exhaust valve by changing a relative rotation phase between a crankshaft and a camshaft of an internal combustion engine for a vehicle. The intake valve or an exhaust valve is driven by the camshaft.
JP 2009-515090A (US 2007/0095315A) describes a valve timing controller in which a vane rotor is rotatable relative to a housing. The valve timing controller includes an oil pressure control valve at a rotation central part of the vane rotor and the camshaft. The oil pressure control valve controls oil passages so that oil is supplied from an oil pump to an advance chamber or a retard chamber defined in the housing. Thereby, the valve timing controller can control the relative rotation phase between the housing and the vane rotor.
A spring is provided for biasing the intake valve or exhaust valve in a valve-closing direction. While the valve timing controller carries out a phase control in a first direction, when torque acts on the camshaft from the spring in a second direction opposite from the first direction, oil may flow backwards from the advance chamber or retard chamber toward the oil pump. The oil pressure control valve of JP 2009-515090A has a valve seat defined by an inner wall of an oil passage to which oil is supplied from the oil pump, a ball valve seated on or separated from the valve seat, and a spring which biases the ball valve toward the valve seat. In case where oil flows backwards from the advance chamber or retard chamber toward the oil pump, when an oil pressure applied to the ball valve from a side of the oil pump becomes smaller than the force of the spring, the ball valve is seated on the valve seat. Thus, the backflow of oil and an unintentional movement of the vane rotor caused by the cam torque are prevented.
However, the valve-closing responsivity may be worse in the oil pressure control valve in case where the oil flows backwards, since the ball valve is seated on the valve seat by the elastic force of the spring.
Moreover, pressure loss may arise in oil flowing to the advance chamber or retard chamber when oil is supplied to the advance chamber or retard chamber from the oil pump, because the oil pressure is applied to the spring which biases the ball valve.
Furthermore, the number of components necessary for producing the oil pressure control valve is increased, and the structure of the oil pressure control valve becomes complicated, due to the spring which biases the ball valve.